There are many medical procedures which require the introduction of a cannula or catheter into a major artery or vein for diagnostic purposes. Angioplasty, for example, is a procedure used to treat cardiovascular disease which involves the introduction of a catheter into the common femoral or brachial artery.
Several methods for introducing a catheter into a blood vessel are known in the art. Two such methods include the "cut down" method and the more recent "Seldinger" technique. The cut down method involves surgically opening an artery and introducing a catheter directly into the incision.
The Seldinger technique involves percutaneously inserting a guidewire and a series of cannulas within the lumen of a blood vessel. For angioplasty in particular, a modification of the Seldinger technique, involving the following steps, is employed.
An introducer sheath is introduced into the lumen of the common femoral or brachial artery. A diagnostic catheter with an indwelling guidewire is inserted within the sheath and is advanced through the vessel to the location of the arterial stenosis or occlusion. Once across the stenosis or occlusion, the diagnostic catheter is removed over the guidewire and an angioplasty balloon catheter is placed onto the guidewire and advanced along the length of the wire to the occluded area. The balloon catheter is then inflated with an appropriate medium to recanalize the occluded artery. After a predetermined period of time, the balloon catheter is deflated and removed over the guidewire. The guidewire is usually left within the vessel to reaccess the occluded area if needed. Typically, the angioplasty procedure is evaluated by injecting a radio-opaque fluid into the once-occluded or stenotic artery. This is accomplished by introducing a second catheter and guidewire assembly into the introducer sheath beside the already existing guidewire.
In order to avoid excessive bleeding and air embolisms during the evaluation procedure, the Seldinger technique requires that the Interventional Radiologist block the open end of the introducer sheath. As a result of this reliance upon the radiologist's manual dexterity, the Seldinger technique is often characterized by blood clots, excessive blood loss, venous thrombosis or subcutaneous hematomas.
In an effort to reduce these adverse conditions, several self-sealing introducer sheaths have been developed. For example, U.S. Pat. No. 4,610,665 to Matsumoto et al. discloses a medical instrument having a valve body. The valve body is provided with first and second slits which are openable to receive rod-like members of varying diameters. The valve maintains a liquid-tight state when a rod-like member is inserted through or removed from the main portion of the instrument.
Similarly, U.S. Pat. No. 4,929,235 to Merry et al. discloses an introducer sheath having a sealing mechanism which includes two spaced sealing gaskets adapted to surround a tube. The gaskets are formed from rubber and include a hole or slit.
Still another example of a self-sealing introducer sheath may be found in U.S. Pat. No. 5,000,745 to Guest et al. The Guest et al. patent discloses an introducer sheath having a valve assembly which includes three elastic disc-shaped membranes to sealingly receive a catheter over a guidewire. Each of the three discs is provided with a different type of opening to accommodate passage of a guidewire and catheter therethrough.
Unfortunately, the above-described devices are not well suited for inhibiting blood loss when a catheter is inserted within an introducer sheath beside an existing guidewire (such as when the angioplasty procedure is being evaluated). The valves of each of the above-described devices are incapable of conforming to the outer surfaces of both a guidewire and a catheter placed within an introducer sheath in a side-by-side manner. Thus, there exists a need for a device which prevents blood loss during all stages of the angioplasty procedure.